This patent document relates to welding systems, devices, and processes.
Welding in large industrial applications, e.g., metal inert gas (mig) and tungsten inert gas (TIG) pipe or plate welding, can involve welding together very thick work pieces in e.g., an orbital welding process. For example, the arc weld head in an orbital welding process can be rotated along a guide track around the work piece, e.g., continuously rotating the welding head 360° around the work piece such as a pipe, or rotating the head around the pipe for 180° on one side of the pipe and then repeating head rotation on the other side of the pipe. Many welding applications require precision welding, from the small standard workpieces to those of the larger scale. Welding systems can be designed to include a welding head and a guide track to which the welding head is movably engaged, e.g., the welding head can be mounted on tractor drive unit, to move along the guide track. For example, some orbital welding systems can have the guide track in a ring or orbital configuration that is engaged around a workpiece to guide the welding head to move along the weld gap. To fit the guide track around the workpiece, several track segments may be joined together to form the full guide track and to securely attach the guide track to the work piece, e.g., 360° around the work piece.
Accordingly, in conventional welding systems, the quality of a weld can be affected by the manner in which a tractor unit is mounted onto a guide track because the mounting can affect how smoothly the tractor unit will travel along the guide track. For example, an improperly mounted tractor unit on a track ring can flex as it moves around the track ring. The flexing can cause the tungsten electrode of the weld head that is attached to the tractor unit to move, e.g., the tungsten electrode can angle in when the tractor unit is at the “12 o'clock” position and angle out when it is at the “6 o'clock” position. This can occur when the tractor unit is not firmly mounted on the track, causing “crabbing” based on vibration or jerking. Additionally, mounting mechanisms can be fragile and easily damaged, e.g., binding and damage to tractor unit components can occur due to over-tightening.
In addition, improper alignment of the travel drive gear in the tractor unit to the track gear of the guide track can also cause problems with weld quality and delays in the welding process. For example, if the center of gravity of the weld head shifts due to, e.g., debris on the track gear, the gears on the travel drive gear and track gear can jam, especially if the system was not properly aligned. To reduce the problems associated with misalignment of the travel drive gear to the track gear, the travel speed of conventional tractor units may need to be set to slow.
Moreover, the mounting of the tractor unit onto guide track may be cumbersome due to the weight of the tractor unit. Typically, the rollers/wheels on a tractor unit need to be manually aligned before the rollers/wheels can engage and clamp onto the guide track. That is, as the tractor unit is being mounted on the guide track, an operator may need to physically jog the tractor unit back and forth while adjusting the engaging mechanism until the rollers/wheels of the tractor unit are properly aligned to the guide track. Because tractor units are relatively heavy, the mounting process may be physically exhausting, especially if the operator has to fight gravity while mounting the tractor unit.
Further, the orientation of electrode relative to the weld puddle and the arc length are important to producing proper welds, especially when mechanical oscillation is used. However, conventional systems and methods for orienting welding heads are not ideal in that they can produce poor quality welds. For example, FIG. 12 illustrates a prior art system for performing a fillet weld using a gas-shielded tungsten arc welding (GTAW) system (50). For brevity, only the components relevant to this discussion are illustrated. The GTAW system (50) includes a welding torch (10) that is oriented such that the torch (10) is, for example, perpendicular to the surface of weld puddle (40) as shown by line (12). The torch (10) is connected to a welding base (30) that provides mechanical oscillation as shown by arrow (32). As the torch (10) is moved across the weld puddle (40), the length of arc (5) will change, i.e., the distance between the tip of tungsten electrode (15) and the surface of weld puddle (40) will change. Accordingly, to maintain the proper arc length, an arc voltage control (AVC) assembly (20) moves torch (10) in the appropriate direction along arrow (22) as the mechanical oscillation moves the torch (10) in a direction (32). That is, the AVC assembly (20) adjusts the distance between the torch (10) and the weld puddle (40) in order to maintain the arc (5) at the desired length. However, because the AVC assembly stroke direction as illustrated by arrow (22) is different from the orientation of the torch (10) as illustrated by line (12), the resulting weld, can be of poor quality. In addition, poor quality welds can also occur due to limited AVC stroke (e.g., limited to approximately 1 inch AVC stroke) and/or limited rotation of the AVC assembly (e.g., limited to approximately 40 degrees) with respect to the welding torch and/or the workpiece (weld puddle). Further, poor quality welds can also occur if the attachment between the welding torch and AVC assembly and/or the attachment between the AVC assembly and the base unit are not stable due to being, e.g., insecure and/or weak and/or if the attachments have excessive wear due to, e.g., overuse and/or lack of durability.
Moreover, in conventional welding systems, the torch electrode lead/lag angle adjustment is limited, typically in the 0 to 5° range with some up to 12°. The limited lead/lag adjustment also limits the flexibility in setting up the welding configuration. In addition, the torch lead/lag adjustment mechanisms in conventional systems have numerous disadvantages such as: marring of weld head components, slippage of the weld head setup due to weak locking mechanisms, difficulty in accessing the lead/lag angle setup mechanisms, and inconsistent lead/lag angle settings—to name just a few.
Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such approaches with embodiments of the present invention as set forth in the remainder of the present application with reference to the drawings.